1. Field of the Invention
The present invention relates to an optical lens system for taking image, and more particularly to a miniaturized optical lens system for taking image used in a mobile phone camera.
2. Description of the Prior Art
In recent years, with the popularity of the mobile phone camera, the optical lens system for taking image has become thinner and thinner, and the electronic imaging sensor of a general digital camera is typically a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor. Due to advances in semiconductor manufacturing, the pixel size of sensors has been reduced continuously, and miniaturized optical lens systems for taking image have increasingly higher resolution. Therefore, there's increasing demand for image quality.
A conventional mobile phone camera, such as the optical lens system for taking image described in U.S. Pat. No. 7,145,736, usually consists of three lens elements, from the object side to the image side: a first lens element with positive refractive power, a second lens element with negative refractive power and a third lens element with positive refractive power. The refractive power arrangement of the lens elements is favorable to correct various aberrations caused by the system, however, the second lens element is a negative lens element and the refractive power of the third lens element is generally small. So in order to provide the refractive power required by the optical lens system, the refractive power of the first lens element must be increased. As a result, the sensitivity of the optical lens system will be increased comparatively, such that the production yield of the optical lens system is reduced.
An optical lens system for taking image which uses lens elements made of glass and plastic is described in U.S. Pat. No. 6,490,102, wherein the third lens element is a spherical glass lens element. The use of the spherical lens element reduces the degrees of freedom available for correcting the off-axis aberration of the optical lens system, making it more difficult to control image quality.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.